This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2001-246583, filed on Aug. 15, 2001; the entire contents of which are incorporated herein by reference.
This invention relates to a magnetoresistance effect element, magnetic head and magnetic reproducing apparatus, and more particularly, to a magnetoresistance effect element structured to flow a sense current perpendicularly of the film surface of a magnetoresistance effect film, as well as a magnetic head and a magnetic reproducing apparatus using the magnetoresistance effect element.
Read-out of information recorded in a magnetic recording medium conventionally relied on a method of moving a reproducing magnetic head having a coil relative to the recording medium and detecting a current induced in the coil by electromagnetic induction then generated. Later, a magnetoresistance effect element was developed, and has been brought into practical use as a magnetic field sensor as well as a magnetic head (MR head) incorporated in a magnetic reproducing apparatus such as a hard disk drive.
For years, magnetic recording mediums have been progressively downsized and enhanced in capacity, and the relative speed between the reproducing magnetic head and the magnetic recording medium during information read-out operation has been decreased accordingly. Under the circumstances, there is the increasing expectation for MR heads capable of extracting large outputs even with small relative speeds.
As an answer to the expectation, it has been reported that multi-layered films, so called an xe2x80x9cartificial lattice filmsxe2x80x9d, which are made by alternately depositing ferromagnetic metal films and nonmagnetic metal films, such as the combination of Fe layers and Cr layers or the combination of Fe layers and Cu layers, under certain conditions, and bringing closely located ferromagnetic metal films into antiferromagnetic coupling, exhibit giant magnetoresistance effects (see Phys. Rev. Lett. Vol. 61, p2474 (1988), Phys. Rev. Lett., Vol. 64, p2304 (1990), for example). Artificial films, however, need a large magnetic field for magnetic saturation, and are not suitable as film materials for MR heads.
On the other hand, there are reports about realization of a large magnetoresistance effect by using a multi-layered film of the sandwich structure of a ferromagnetic layer on a nonmagnetic layer and a ferromagnetic layer even when the ferromagnetic layer is not under ferromagnetic coupling. According to this report, one of two layers sandwiching the nonmagnetic layer is fixed in magnetization beforehand by application of an exchanging bias magnetic field thereto, and the other ferromagnetic layer is magnetically reversed with an external magnetic field (signal magnetic field, for example). It results in changing the relative angle between the magnetization directions of these two ferromagnetic layers on opposite surfaces of the nonmagnetic layer, and exerting a large magnetoresistance effect. The multi-layered structure of this kind is often called xe2x80x9cspin valvexe2x80x9d (see Phys. Rev. B, Vol. 45, p806 (1992), J. Appl. Phys., Vol. 69, p 4774 (1981) and others).
Spin valves that can be magnetically saturated under a low magnetic field are suitable as MR heads and are already brought into practical use. However, their magnetoresistance ratios are only 20% maximum. Therefore, to cope with area recording densities not lower than 100 Gbpsi (gigabits per square inch), there is the need of a magnetoresistance effect element having a higher magnetoresistance ratio.
Structures of magnetoresistance effect elements are classified into CIP (current-in-plane) type structures permitting a sense current to flow in parallel to the film plane of the element and CPP (current-perpendicular-to-plane) type structures permitting a sense current to flow perpendicularly to the film plane of the element. Considering that CPP type magnetoresistance effect elements were reported to exhibit magnetoresistance ratios as large as approximately ten times those of CIP type elements (J. Phys. Condens. Mater., Vol. 11, p. 5717 (1999) and others), realization of the magnetoresistance raio of 100% is not impossible.
However, CPP type elements having been heretofore reported mainly use artificial lattices, and a large total thickness of films and a large number of boundary faces caused a large variation of resistance (absolute output value). To realize a satisfactory magnetic property required for a head, the use of a spin valve structure is desirable.
FIG. 30 is a cross-sectional view that schematically showing a CPP type magnetoresistance effect element having a spin valve structure. A magnetoresistance effect film M is interposed between an upper electrode 52 and a lower electrode 54, and a sense current flows perpendicularly to the film plane. The magnetoresistance effect film M shown here has the basic film structure sequentially made by depositing a base layer 12, antiferromagnetic layer 14, magnetization-pinned layer 16, nonmagnetic intermediate layer 18, magnetization free layer 20 and protective layer 22 on the lower electrode 54.
As these layers are basically made of metals. The magnetization-pinned layer (called pinned layer) is a magnetic layer in which magnetization is fixed substantially in one direction. The magnetization free layer 20 (called free layer) is a magnetic layer in which the direction of magnetization can freely change depending upon an external magnetic field.
This kind of spin valve structure, however, has a smaller total thickness and fewer boundary faces than those of artificial lattices. Therefore, if a current is supplied perpendicularly to the film plane, then the resistance becomes small and the absolute output value becomes smaller.
For example, if a spin valve film having a film structure heretofore used in a CIP structure is directly used in a CPP structure and a current is supplied perpendicularly of the film plane, the absolute value of the output per 1 xcexcm2, Axcex94R, is only about 1 mxcexa9xcexcm2. That is, for practically using a CPP using a spin valve film, increase of the output is an important issue. For this purpose, it is very effective to increase the resistance value of a portion of the magnetoresistance effect element taking part in spin-dependent conduction and thereby increase the resistance change.
Output of a CPP type magnetoresistance effect element is determined by spin-dependent scattering along the interface between a magnetic layer and a nonmagnetic layer (interface scattering) and spin-dependent scattering in the magnetic layer (bulk scattering). Taking it into account, a large output increase can be expected by using a material exhibiting large spin-dependent interface scattering to form the interface with the nonmagnetic layer and using a material exhibiting large spin-dependent bulk scattering to form the substantial part occupying the majority part of the magnetic layer.
If a nonmagnetic back layer is inserted along one of interfaces of the magnetically pinned layer or magnetically free layer not contacting the nonmagnetic intermediate layer, spin-dependent interface scattering along the interface between the pinned layer and the nonmagnetic back layer or the interface between the free layer and the nonmagnetic back layer can be used. Thus, if a material exhibiting large spin-dependent interface scattering is used to form the interface between the pinned layer and the nonmagnetic back layer or between the free layer and the nonmagnetic back layer, the output increases.
Insertion of a different material in a location within the pinned layer or the free layer results in bringing a modulation in the band structure, and it may possibly increase the output.
The Inventors proceeded with their own trial and researches from that point of view, and reached the invention of the unique magnetoresistance effect element explained below.
According to the embodiment of the invention, there is provided a magnetoresistance effect element comprising:
a magnetoresistance effect film including a magnetically pinned layer having a magnetic material film whose direction of magnetization is pinned substantially in one direction, a magnetically free layer having a magnetic material film whose direction of magnetization changes in response to an external magnetic field, and a nonmagnetic metal intermediate layer located between said pinned layer and said free layer; and
a pair of electrodes electrically connected to said magnetoresistance effect film to supply a sense current perpendicularly to a film plane of said magnetoresistance effect film,
at least one of said pinned layer and said free layer including a thin-film insertion layer.
The thin-film insertion layer may be made of an alloy containing at least two kinds of metals among iron (Fe), cobalt (Co) and nickel (Ni) as matrix elements thereof, and in case of a binary alloy, said alloy containing each of said two kinds of matrix elements by not less than 25 atomic % respectively, and in case of a ternary alloy, said alloy containing each of said three kinds of matrix elements by not less than 5 atomic % respectively.
The thin-film insertion layer may alternatively be made of a binary alloy or a ternary alloy containing at least two kinds of metals among iron (Fe), cobalt (Co) and nickel (Ni) as matrix elements thereof, and additionally containing a quantity of at least one kind of element selected from the group consisting of chromium (Cr), vanadium (V), tantalum (Ta), niobium (Nb), scandium (Sc), titanium (Ti), manganese (Mn), copper (Cu), zinc (Zn), gallium (Ga), germanium (Ge), zirconium (Zr), hafnium (Hf), yttrium (Y), technetium (Tc), rhenium (Re), ruthenium (Ru), rhodium (Rh), iridium (Ir), palladium (Pd), platinum (Pt), silver (Ag), gold (Au), boron (B), aluminum (Al), indium (In), carbon (C), silicon (Si), tin (Sn), calcium (Ca), strontium (Sr), barium (Ba), oxygen (O), nitrogen (N) and fluorine (F) not less than 0.1 atomic % and not exceeding 30 atomic %.
The thin-film insertion layer may alternatively be a binary alloy containing a quantity of iron (Fe) not less than 50 atomic % as the major component thereof, or a ternary alloy containing a quantity of iron (Fe) not less than 25 atomic % as the major component thereof, and said alloy having a body-centered cubic crystal structure.
The thin-film insertion layer may alternatively be made of iron (Fe) having a body-centered cubic crystal structure.
The thin-film insertion layer may alternatively be made of an alloy containing iron (Fe) and chromium (Cr) as major components thereof and adjusted in quantity of chromium (Cr) in the range from 0 atomic % to 80 atomic %, said alloy having a body-centered cubic crystal structure.
The thin-film insertion layer may alternatively be made of an alloy containing iron (Fe) and vanadium (V) as major components thereof and adjusted in quantity of vanadium (V) in the range from 0 atomic % to 70 atomic %, said alloy having a body-centered cubic crystal structure.
The thin-film insertion layer may alternatively be made of iron (Fe), or a binary or ternary alloy of iron (Fe), cobalt (Co) and nickel (Ni) containing a quantity of iron (Fe) not less than 50 atomic % in case of said binary alloy or 25% atomic % in case of said ternary alloy, and additionally containing a quantity of at least one kind of element selected from the group consisting of chromium (Cr), vanadium (V), tantalum (Ta), niobium (Nb), scandium (Sc), titanium (Ti), manganese (Mn), copper (Cu), zinc (Zn), gallium (Ga), germanium (Ge), zirconium (Zr), hafnium (Hf), yttrium (Y), technetium (Tc), rhenium (Re), ruthenium (Ru), rhodium (Rh), iridium (Ir), palladium (Pd), platinum (Pt), silver (Ag), gold (Au), boron (B), aluminum (Al), indium (In), carbon (C), silicon (Si), tin (Sn), calcium (Ca), strontium (Sr), barium (Ba), oxygen (O), nitrogen (N) and fluorine (F) not less than 0.1 atomic % and not exceeding 30 atomic %.
The thin-film insertion layer may alternatively be made of cobalt (Co), or a binary or ternary alloy of iron (Fe), cobalt (Co) and nickel (Ni) containing a quantity of cobalt (Co) not less than 50 atomic % in case of said binary alloy or 25% atomic % in case of said ternary alloy, and additionally containing a quantity of at least one kind of element selected from the group consisting of chromium (Cr), vanadium (V), tantalum (Ta), niobium (Nb), scandium (Sc), titanium (Ti), manganese (Mn), copper (Cu), zinc (Zn), gallium (Ga), germanium (Ge), zirconium (Zr), hafnium (Hf), yttrium (Y), technetium (Tc), rhenium (Re), ruthenium (Ru), rhodium (Rh), iridium (Ir), palladium (Pd), platinum (Pt), silver (Ag), gold (Au), boron (B), aluminum (Al), indium (In), carbon (C), silicon (Si), tin (Sn), calcium (Ca), strontium (Sr), barium (Ba), oxygen (O), nitrogen (N) and fluorine (F) not less than 0.1 atomic % and not exceeding 30 atomic %.
The thin-film insertion layer may alternatively be made of nickel (Ni), or a binary or ternary alloy of iron (Fe), cobalt (Co) and nickel (Ni) containing a quantity of nickel (Ni) not less than 50 atomic % in case of said binary alloy or 25% atomic % in case of said ternary alloy, and additionally containing a quantity of at least one kind of element selected from the group consisting of chromium (Cr), vanadium (V), tantalum (Ta), niobium (Nb), scandium (Sc), titanium (Ti), manganese (Mn), copper (Cu), zinc (Zn), gallium (Ga), germanium (Ge), zirconium (Zr), hafnium (Hf), yttrium (Y), technetium (Tc), rhenium (Re), ruthenium (Ru), rhodium (Rh), iridium (Ir), palladium (Pd), platinum (Pt), silver (Ag), gold (Au), boron (B), aluminum (Al), indium (In), carbon (C), silicon (Si), tin (Sn), calcium (Ca), strontium (Sr), barium (Ba), oxygen (O), nitrogen (N) and fluorine (F) not less than 0.1 atomic % and not exceeding 30 atomic %.
The thin-film insertion layer may alternatively be made of a iron (Fe)-cobalt (Co)-system alloy having a body-centered cubic crystal structure, and additionally containing a quantity of at least one kind of element selected from the group consisting of chromium (Cr), vanadium (V), tantalum (Ta), niobium (Nb), scandium (Sc), titanium (Ti), manganese (Mn), copper (Cu), zinc (Zn), gallium (Ga), germanium (Ge), zirconium (Zr), hafnium (Hf), yttrium (Y), technetium (Tc), rhenium (Re), ruthenium (Ru), rhodium (Rh), iridium (Ir), palladium (Pd), platinum (Pt), silver (Ag), gold (Au), boron (B), aluminum (Al), indium (In), carbon (C), silicon (Si), tin (Sn), calcium (Ca), strontium (Sr), barium (Ba), oxygen (O), nitrogen (N) and fluorine (F) not less than 0.1 atomic % and not exceeding 10 atomic %.
The thin-film insertion layer may alternatively be made of a iron (Fe)-cobalt (Co)-system alloy having a body-centered cubic crystal structure, and layers made of at least one kind of element selected from the group consisting of chromium (Cr), vanadium (V), tantalum (Ta), niobium (Nb), scandium (Sc), titanium (Ti), manganese (Mn), copper (Cu), zinc (Zn), gallium (Ga), germanium (Ge), zirconium (Zr), hafnium (Hf), yttrium (Y), technetium (Tc), rhenium (Re), ruthenium (Ru), rhodium (Rh), iridium (Ir), palladium (Pd), platinum (Pt), silver (Ag), gold (Au), boron (B), aluminum (Al), indium (In), carbon (C), silicon (Si), tin (Sn), calcium (Ca), strontium (Sr), barium (Ba), oxygen (O), nitrogen (N) and fluorine (F) having a thickness not thinner than 0.03 nm and not exceeding 1 nm which permits said layers to exist as a body-centered cubic structure being periodically inserted in said alloy.
The nonmagnetic metal intermediate layer may have a resistance adjusting layer including at least one of oxides, nitrides and fluorides, and the thin-film insertion layer may include at least one element selected from the group consisting of iron (Fe), cobalt (Co) and nickel (Ni).
At least one of the pinned layer and said free layer may have a resistance adjusting layer including at least one of oxides, nitrides and fluorides, and the thin-film insertion layer may include at least one element selected from the group consisting of iron (Fe), cobalt (Co) and nickel (Ni).
A magnetic head according to the embodiment of the invention may comprise a magnetoresistance effect element having any one of the above-mentioned features.
A magnetic reproducing apparatus which reads information magnetically recorded in a magnetic recording medium according to the embodiment of the invention may comprise a magnetoresistance effect element having any one of the above-mentioned features.